I have tried looking for this information without any luck, so I figured I would ask for my specfic project.

I am in the process of building a VQ30 and have decided against the VQ35 Swap. However, I would like to use the Cylinder Heads of the VQ35 because of the better flow capabilities.

Will the VQ35 Heads bolt right on to the VQ30 Block or will modification be needed? If so what needs to be modified?

I would like to incorporate this setup with my Custom VQ30 Rods and 9:1 Pistons. This Engine is being built for boost via a turbo setup.

Are there any downfalls to this setup, will using these heads alter my compression ratio or anything else, and if so will it be even more so altered if used with 9:1 pistons?

Thanks.

JP

 

i dont know about the bolting on, im pretty sure they bolt on, some things on top may need fabrication though. as far as compression, it will be ,lower since the 3.5 heads have larger cumbustion chambers. if you plan to do a lot of boost using these heads is better, since they will flow better, lower compression ratio so you can use more boost, less likely to detonate and some other things im sure

 

Downfall would be that VQ35 heads on VQ30 block drops the compression, and then you are going to drop the compression even more with your low comp pistons. I could do the calculations to figure out what the resulting compression would be but I just worked 13 hours and I don't feel like it. My guess would be like 7.7:1 off the top of my head, obviously wayyyy lower than you would want it if I'm anywhere close to correct.

 

I wouldn't do it. The piston and cylinder head are designed in such a way that as the air/fuel mixture is squished it's forced to the center of the combustion chamber where the spark plug is for consistent and efficient combustion, aka squish area. Since the diameter of the 3.5 heads is larger than that of the 3.0 block there's a chance that some of the air/fuel mixture will sneak off to the outer edges and not get burned completely. Hope that makes sense...

 

Thanks for the input so far.

Nealoc: I was thinking that my compression ratio would drop to an unusable rate. If you find the time would you mind doing a couple calculations? I also have a 10:1 or a 10.5:1 compression ratio piston to choose from, would any of those be better off?

Also on a side note: Does the bore of the pistion have any affect on the flow of the Cylinder head? I have a choice of a stock bore of 93mm to 94mm.

Thanks!

JP

 

the only difference bore makes in flow is that it sucks in more air because it has a larger cylinder volume. if you can use the 10:1 or 10.5:1 pistons i think the 3.5 heads might be worth using because they are better than the 3.0 heads and with the higher compression pistons you will still have reasonable compression ie 8.5:1 or more. thats not low compression at all, in fact, some NA engines run at that compression

 

sounds great if you are gonna boost, right?

 

There is no need to build a VQ30 or consider swapping a VQ35 in a turbo car unless you start blowing motors from power. If you are not even set up with your turbo kit, then get it and you fuel/tuning running correctly and then worry about your motor. You would be surprise at what a correctly setup VQ30 can take.

To use VQ35 heads you would have to buy a VQ35. Thus a full swap would cost the about same. VQ35 pistons and rods are pretty cheap (cheaper than custom VQ30 rods) and easy to find. Thus it is probably not worth it to build a VQ30 for turbo use.

VQ35 heads fit fine on there. Just use a VQ35 head gasket. The 350Z OEM or aftermarket would be a good idea along with ARP head studs. The CR would drop to ~9.0-8.8:1 so lower compression pistons would not be needed.

You should probably just build a VQ32 (VQ35 heads, pistons, block with VQ30 crank and rods) as it seems to be the best of both setups. This is probably the best setup to do without any aftermarket parts.

 

SPiG:

I am well aware of the potential of a properly tuned VQ30. I already have a turbo kit, and have deemed it necessary to build a vq30 for both the reliability and power I hope to accomplish.

Why would I need to purchase an entire VQ35 if I just wanted to use the heads? Yes, If I were in a different situation I would build a VQ35 instead. However the fact that I have a spare VQ30 and custom rods already kind of places me in the situation I am in.

The VQ32 Setup does interest me, and will have to look more into as I know Tilley is the only one to have experienced this setup.

I thank everyone for their input and the information that has been provided thus far.

JP

 

I have two sets of VQ35DE heads for sale, one set from a FWD Maxima motor and one set from a RWD 350Z motor. If anyone is serious about doing this PM me.

allen

 

If I were to use these heads, what C/R Piston should I use: 10:1 or 10:5:1
also should I stay with the stock bore or use 94mm.

Just out of curiousity is it true, that if the bore is increased the compression ratio would also increase?

Thanks for the help.

JP

 

depends on if youre going to boost or not. with boost, lower compression means you can have a lot more boost, without boost higher compression is good to a certain point

 

You must not have read the rest of the thread, the motor is being built for boost and because the VQ35 Heads lower the C/R I was looking to see which of the two options would provide me with the more ideal C/R afterwards.

JP

 

i wasnt thinking, thought you were someone other than thread starter. how i understand it, the lower the compression ratio the more boost you can run, so it depends on how much boost you want. the VG30DETT ran about 9:1 so like spig said, if you use the higher compression pistons you should have around there, which would be a pretty good place to be.